Engine O-Rings Produced Using Additive Manufacturing

Additive Manufacturing (AM) using stereolithography (SLA) was applied to produce engine O-rings using two different flexible polymer printing materials, Flex 80A and Elastic 50A. Print orientation of the O-ring in the SLA 3D printer is important, with the horizontal configuration most commonly providing for the smoothest final O-ring printed surface due to the lack of printing support tabs required. AM printing tabs lead to O-ring ‘marks’ (non-smooth surfaces) that were evaluated using the Society of Automotive Engineers SAE AS871B standard. It was seen that numerous printing approaches produced ‘marks’ that were larger than acceptable, which shows that these studied AM processes can not replace traditional methods of O-ring manufacture. However, further evaluation was pursued to explore possible remote emergency usage of these O-rings.

Printed O-rings were next tested-soaked in engine related fluids in order to characterize O-ring swelling behavior. Volume swelling was greatest with acetone (100% plus increase) for both the stock O-rings tested and moderately less so with the 3D printed O-rings. Flex 80A printing material swelling was moderately less than using Elastic 50A printing material. Swell testing using motor oil and engine fuels showed significantly less swelling with volume change increases on the order of ten to fifteen percent. Pressure vessel and engine-based testing was also performed with the printed O-rings demonstrating good performance (no leaks) under operation, suggesting that shorter term emergency-based operation using these AM printed O-rings may be acceptable.